The present invention relates to a screw, more particularly a screw, which is formed with several cutting trenches on the rod-shaped portion thereof for allowing cut-off bits of a workpiece to be deposited in to reduce resistance of the bits of wood when screwed into the workpiece.
A conventional screw includes a front-end screw-in portion and a straight portion. The screw-in portion tapers off towards a pointed end. A continuous spiral-shaped thread is formed on both the screw-in portion and the straight portion so that the screw can be screwed into a workpiece. However, the screw is likely to cause cracks on the workpiece because the screw is forced into the same without cutting off bits of the workkpiece. And, the screw is subject to excessive resistance of the workpiece.
To overcome the disadvantages of the above conventional screw, referring to FIGS. 10, and 11, an improvement 2 on the screw was provided which is formed with cutting trenches 22 on the outward edge of the spiral thread 21 such that bits of a workpiece can be cut off from the spiral passage in the wokpiece that is formed by the thread when the screw is being screwed into the same. However, it is found that cut-off bits of workpiece will very quickly fill the cutting trenches 22 that have very limited capacity, becoming an undesirable resistance against the screw.
Therefore, it is a main object of the present invention to provide a screw, which is shaped in such a manner as to be able to be screwed into a workpiece easily and without causing cracks on the workpiece while the tightness of connection is not reduced.
The screw of the present invention includes a rod-shaped portion, and a spiral-shaped thread winding around the rod-shaped portion. Several cutting trenches are formed on the rod-shaped portion for cutting bits off a workpiece with which when the screw is being screwed into the same. A tapering front end portion of the rod-shaped portion is provided with a notch, and cutting teeth are provided on that portion of the thread corresponding to the tapering front end portion. Cut-off bits of a workpiece can be received in the trenches as well as the cutting teeth so as to have reduced resistance against the screw, thus allowing the screw to be screwed into the workpiece relatively easily without possibility of causing cracks on the workpiece.